1. Field of the Invention
The present invention relates to an image reading apparatus, such as a scanner for reading the image of an original, and a control method therefor, as well as a storage medium.
2. Description of the Related Art
When reading the image of an original, a standardized size corresponding to the size of the original or the like is specified as a reading size for an image reading apparatus such as a scanner or the like. On the other hand, there is a growing demand for image reading of batch of originals in which originals of different sizes are mixed. Accordingly, there has been proposed an image reading apparatus having a function of automatically discriminating the size of an original being read.
This discrimination function is preferably used for performing image reading of batch of originals in which originals of different sizes are mixed. The discrimination function is not limited to this application but is effectively used also in a case where an original of a standardized size is read so as to eliminate the need for such efforts as selecting a size when reading an image. In general, the inherent color of an original is white or substantially white. Hence, there is known a method for detecting the image size by changing a background member arranged opposite to an image sensor to a black-colored background member and detecting a black part included in periphery of the read image data.
As an image size detecting method performed in a case where the color of a background member is set to white or substantially white, there has been proposed a method for discriminating the size of an original using a shadow produced by illumination (see Japanese Laid-Open Patent Publication (Kokai) No. 2001-285585, for example). In addition, there has been disclosed a configuration in which an illumination source and an image sensor are disposed opposite to each other across a conveyance path of originals, in order to detect the skew of an original (see Japanese Laid-Open Patent Publication (Kokai) No. H06-339007). Furthermore, there has been disclosed a method in which a read image based on reflected light and a transmissive image based on transmitted light are obtained using one illumination source and two image sensors arranged on both sides of the conveyance path of originals, thereby allowing removal of a show-through image developed in the read image using the transmissive image data (see Japanese Laid-Open Patent Publication (Kokai) No. 2002-281257, for example).
In Japanese Laid-Open Patent Publication (Kokai) No. 2001-285585 described above, however, since the size of an original is detected using information on the shadow produced by illumination, the accuracy of original size detection may degrade due to false operation if any black part is present in the outermost area of the original.
In addition, according to the methods disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H06-339007 described above, though it is possible to identify the size of an original, there arises the need to arrange a dedicated image sensor or sensors, thus leading to an increase in the size and cost of an image reading apparatus. In addition, the methods disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2002-281257 described above, does not intend to identify the size of an original.